Websites operated by the Japanese government and the nation’s biggest defence contractor have been targeted by cyber attacks at the weekend that apparently originated in China, according to the National Police Agency.

The attacks took place on Saturday and Sunday – the 80th anniversary of the Manchurian Incident, which led to the Japanese invasion of northern China – and affected the sites of the National Personnel Authority, the Cabinet Office and a government video distribution service.

The disruption was in the form of denial-of-service attacks, in which hackers transmit huge amounts of data to a site in order to overwhelm its capacity to function.

The agency said 90 per cent of the attacks had been traced back to China, where earlier online messages had been calling for attacks on Japanese sites to mark the anniversary of the 1931 Manchurian Incident.